Big Spender (http://www.imdb.com/title/tt0356414/)
Orphan Eddie Burton is not bad, but too many screw-ups land him repeatedly in jail, so his 8-year old son Will, simply abandoned by his 'mother', has nobody else then Eddie's granny.
When he hears about a program for convicts working an a foundation's farm for retired race horses, Eddie signs up and proves his talent with Big Spender, who was found completely run down. He nurses the horse back to health, and convinces
Jake Cotter, the man in charge, to try a stunt: train him for an new career in jumping, which is a success when his dedicated race jockey Mel Tennant volunteers to ride him again.
If he does really well, he may even get a certificate opening the perspective of a real job, which he desperately needs when grandma dies after having him swear he'll get out: the nightmare alternative is to leave Will lingering in the very home that did Eddie no good.